move vfs to fs dir

fs/ident.c

@@ -0,0 +1,17 @@
+#include <zinnia/ident.h>
+
+static const struct ident kernel_identity = {0};
+
+const struct ident* ident_kernel() {
+    return &kernel_identity;
+}
+
+bool ident_in_group(const struct ident* identity, gid_t gid, bool use_real) {
+    if (gid == (use_real ? identity->gid : identity->egid))
+        return true;
+    vec_foreach(&identity->groups, i) {
+        if (vec_elem_get(&identity->groups, i) == gid)
+            return true;
+    }
+    return false;
+}